Fatigue behaviour of concrete bridge deck slabs reinforced with GFRP bars
Valter Carvelli
*
, Marco Andrea Pisani, Carlo Poggi
Department of Structural Engineering, Politecnico di Milano, Piazza Leonardo da Vinci 32, 20133 Milano, Italy
article info
Article history:
Received 11 September 2009
Accepted 12 June 2010
Available online 26 June 2010
Keywords:
A. Glass fibres
B. Fatigue
B. Strength
D. Mechanical testing
abstract
GFRP bars are often used for the internal reinforcement of concrete bridge deck slabs as an alternative to
traditional steel reinforcements with excellent results in terms of corrosion resistance. Several experi-
ments on bridge decks were conducted to evaluate their structural behaviour but their fatigue perfor-
mance still needs an adequate experimental investigation. This paper presents the results of an
experimental campaign on four full scale concrete bridge deck specimens reinforced with GFRP bars that
were designed, constructed and tested to resist cyclic moving loads. Two hydraulic jacks were used to
simulate moving concentrated loads. After the cycles, the load was increased to the static failure. The
slabs reinforced with GFRP bars showed a better fatigue performance compared to the requests of the
European codes.
Ó 2010 Elsevier Ltd. All rights reserved.
1. Introduction
In several cold countries, the temperature fluctuation and the
de-icing that is traditionally done with salt along with sand and
gravel, often cause the corrosion of steel reinforcing bars and af-
fect the durability of bridge decks. The corrosion of steel rebars
causes cracking and spalling of concrete bridge decks with con-
sequent elevated costs for rehabilitation and traffic disruption.
Starting from the early nineties the possibility to replace steel
rebars with GFRP rebars (that resist fairly well to salt water),
as reinforcement of concrete bridge slabs, has been investigated
to increase their service life in these unfavourable conditions
(see e.g. [1]).
The GFRP bars, compared to the traditional steel rebars, present
a lower modulus of elasticity and smaller transverse shear
strength. As a consequence, the overall shear capacity of concrete
members reinforced with GFRP bars is lower than that of an equiv-
alent traditional member reinforced with the same quantity of
steel.
The deck slabs sustain the moving concentrated loads repre-
sented by the wheels of the vehicles, and are therefore susceptible
to fatigue failures. Often, after cracking, the deck slabs support the
traffic loads through arching behaviour. In these cases, compres-
sive membrane forces are generated by the restraining action of
the supporting girders. As a consequence, the slab can reach failure
by local punching under concentrated loads. Several research pro-
jects were carried out to study the effects of the travelling concen-
trated loads on traditional concrete deck specimens reinforced
with steel bars. Okada et al. [2] tested some steel reinforced deck
slabs and found that the formation of wider cracks due to the mov-
ing loads caused a reduction of the shear stiffness of the deck. In
other experiments conducted on reduced scale models [3] it was
shown that the cracking was radial in the case of a single pulsating
load while the crack pattern was of a grid-shape in the case of
moving loads. In the last case both the flexural and shear fatigue
resistance were decreased.
Full scale bridge deck slabs reinforced with GFRP bars were pre-
sented in [4]. No bond loss was detected and the crack pattern was
typical of bending of the concrete deck spanning between the steel
girders. The deck degradation during fatigue was found to be com-
parable to traditional steel reinforced concrete decks. El-Ragaby
et al. [5] tested six full-size GFRP reinforced slabs and found that
the punching shear was the only mode of failure under fatigue
loads. The GFRP reinforced decks had a better fatigue performance
and longer fatigue life compared to those reinforced with steel.
Therefore, it can be stated that the behaviour of these structural
elements reinforced with GFRP bars and subject to moving cyclic
loads is not fully assessed.
The present paper describes experimental tests performed on
full scale bridge slab prototypes (5000 Â 2480 Â 200 mm) rein-
forced with GFRP bars. The specimens are reinforced with 16 mm
diameter GFRP rebars whose external surface is sanded and spi-
rally wounded. The cyclic loads are applied by two hydraulic jacks
alternately pulsating.
The mechanical behaviour of the unidirectional glass fibre rein-
forcing bars was investigated and compared with available exper-
imental data. Bond tests were performed to verify the suitability of
the rebars.
The aim of the research is to verify if the rules suggested by the
European Codes for these structural elements can be extended to
bridge deck slabs reinforced with GFRP rebars and to study their
1359-8368/$ - see front matter Ó 2010 Elsevier Ltd. All rights reserved.
doi:10.1016/j.compositesb.2010.06.006
* Corresponding author. Tel.: +39 02 2399 4354; fax: +39 02 2399 4369.
E-mail address: valter.carvelli@polimi.it (V. Carvelli).
Composites: Part B 41 (2010) 560–567
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